Method of making a capstan



May 6, 1969 M. FURST ET AL 3,441,998

METHOD OF MAKING A CAPSTAN Filed Feb. 9, 1967 INVENTORS RCEL FURST RVIN L. FALK ATTORNEYS United States Patent 3,441,998 METHOD OF MAKING A CAPSTAN Marcel Furst and Mervin L. Falk, Sunnyvale, Calif., as-

signors to Newell Associates, Inc., Sunnyvale, Calif., a

corporation of California Filed Feb. 9, 1967, Ser. No. 614,967 Int. Cl. B21k 1/00 US. Cl. 29-159 2 Claims ABSTRACT OF THE DISCLOSURE Tape roll drive capstan having a periphery wherein the outer margins are harder than intermediate portions so as to eliminate cupping of tape rolls. Method of manufacture obtains the difference in hardness from uniformly homogeneous material.

This invention relates to tape transport apparatus, and more particularly to a method of making a capstan of a type for driving supply and take-up rolls of tape to transfer a length of tape from the former to the latter.

In apparatus for feeding magnetic recording tape, a common problem which is frequently encountered is cupping of the rolls of tape. Briefly, this problem refers to the phenomenon whereby after tape has been fed between supply and take-up rolls a number of times, the rim or edge of the roll becomes somewhat concave as distinguished from the desired rectilinear configuration which it had upon being initially employed. Thus, where the edge of a roll has become concave, cupping exists and introduces deleterious effects to the tape itself as well as serving to introduce well-known problems with respect to transducing signals to and from the tape.

Accordingly, it is readily evident that apparatus for feeding tape from a supply to a take-up roll wherein cupping can be minimized or eliminated becomes highly desirable.

It is a general object of the present invention to provide a capstan construction and method of manufacturing same whereby in the feeding of tape from a supply to a take-up roll cupping of tape rolls is essentially eliminated.

As used herein the term edge driven refers to the edge of the rolls as distinguished from the edges of the tape. Another term for the present arrangement might be rim-driven rolls, but it is readily apparent that the rolls have no rim.

Briefly stated, in the capstan construction disclosed herein, there is provided an annular rotating body adapted to be mounted for rotation. The periphery around the body is adapted to engage and press against the edge of a roll of tape so as to develop reactive forces in the periphery such that these reactive forces act radially outwardly thereof. The capstan construction herein is characterized by the fact that those reactive forces disposed to oppose the longitudinal outer margins of the engaged roll of tape are at least as great as those reactive forces developed in between. According to the method of manufacture disclosed herein, a uniformly homogeneous material can be employed to form the periphery of the capstan.

Other objects of the invention will become readily apparent from the following detailed description of a preferred embodiment, when considered in conjunction with the accompanying drawings, in which:

FIGURE 1 is a view partially in elevation cross-sec tion showing a capstan construction according to the invention and schematically disposed in conjunction with supply and take-up rolls;

FIGURE 2 is an enlarged detail view, in section, of

3,441,998 Patented May 6, 1969 "ice a portion of the capstan construction shown in FIGURE 1 prior to the attachment of flanges thereto;

FIGURE 3 is an enlarged detail view, in section, similar to FIGURE 2 after attachment of flanges thereto;

FIGURE 4 is a further enlarged detail view, in section, of that portion of FIGURE 3 taken along the lines 4-4 thereof;

FIGURES 5 and 6 respectively show rolls of tape with and without the problem of cupping; and

FIGURE 7 is a diagram of the invention showing a detailed portion of FIGURE 1.

There has been provided herein a capstan construction of a type for edge-driving supply and take-up rolls of tape for transferring a length of tape from the former to the latter. Thus, the edges of the rolls are engaged by the capstan periphery. The cylindrical capstan periphery includes a resilient driving surface bounded at the cylindrical end edges to preclude expansion laterally of the driving surface. The back side of the resilient driving surface is supported by a homogeneous body as provided, for example, by a metal hub.

Thus, the capstan construction generally comprises a rigid annular hub adapted to be mounted for rotation. A relatively thin layer of resilient material encircles the hub and is adapted for edge-driving engagement with rolls of tape. A pair of flanges are carried by the ends of the hub and extend radially outwardly across the end edges of the driving layer. The flanges serve to compress the ends of the layer so as to support the layer against any endwise expansion of the layer under applied compression experienced during an edge-driving transfer of tape.

More particularly, referring to the drawings, a supply roll 11 and take-up roll 12 are arranged whereby a capstan assembly 13 can be rotated to transfer tape 14 from hub 16 to take-up roll 12.

Capstan assembly 13 comprises an annular, generally cylindrical, hub 17 of a rigid material, such as cast aluminum. Hub 17 includes a cylindrical periphery 18 having an axial extent essentially co-extensive with the width of tape 14.

Periphery 18 carries a relatively thin layer 19 of resil ient material, preferably polyurethane. The material of layer 19 should be virtually completely free of any bubbles or pockets of porosity whereby uniform density of the material and support of tape is assured.

In the process of manufacturing capstan assembly 13, layer 19 is applied to hub 17, preferably by molding to form a structure as shown in FIGURE 2. Layer 19 is disposed and dimensioned to provide end edges 21, 22. The edges are then reduced down to a point where they overhang the ends 23, 24 of hub 17 only slightly. This is preferably accomplished by grinding edges 21, 22 until the plane of ends 23, 24 is reached. When the grinding tool is removed, the resilience of the material of layer 19 causes edges 21, 22 to spring back an amount suitable for providing the advantageous anti-cupping properties to the capstan. The extent to which edges 21, 22 then extend beyond ends 23, 24 has been found, in the case of a quarter-inch wide periphery 18, of polyurethane, to run on the order of 0.001 inch.

By securing flanges 27, 28 to the ends of hub 17, a bulge 25 is thus formed on the driving surface of layer 19 by the axial compression of the flanges acting on the overhanging portion 26 of layer 19. This step of axially compressing the overhanging portion 26, therefore, serves to form bulge 25. Thereafter, flanges 27, 28 are coupled, as by screws, to the respective ends 23, 24 of hub 17.

Thus, the bounding surface of a side wall member, such as flanges 27, 28 bears against each of the end edges 21, 22 of layer 19 and compresses them in a direction axially of hub 17 so as to form bulge 25 along the edge margins of layer 19.

A capstan construction, as described above, is adpated to be driven by a spindle 29 and mounted for rotation in edge-driving relation to supply and take-up rolls 11, 12. In a particularly preferred embodiment, supply and take-up rolls 11, 12 may be resiliently urged, as by springs 31, 32 toward capstan 13. In this manner compression is applied to the face of layer 19.

A particularly preferred construction of the above arrangement has been built and successfully operated to eliminate cupping (as shown in FIGURE 5) for a one-quarter inch width of magnetic recording tape wherein the thickness of layer 19 ran on the order of 0.0625 to 0.125 inch. It was found that the former dimension may be somewhat too thin to successfully accommodate splices in the tape and run-out found in the roll of tape and therefore represents a minimum thickness.

It has been observed (FIGURE 7) that the reactive forces F must be at least as great as forces F to over- Come the cupping problem completely. Whereas a thickness on the above order represents something of a minimum, there appears to be no particular maximum so long as the reactive forces along the outer margins 36, 37 equal or exceed forces F The material of layer 19 preferably, as noted above, consists essentially of polyurethane and preferably has a hardness within a range on the order of 40-60 durometer (shore A). Using fixed flanges as shown in the drawings, the tape edges of rolls 11, 12 preferably provide a closely spaced fit with the bounding surfaces 33, 34 of flanges 27, 28. Thus, a slight positive spacing between surfaces 33, 34 preferably runs on the order of 0.001 to (-1-) 0.002 inch relative to the Width of tape 14. Accordingly,the axial extent of periphery 18 is substantially coextensive with the width of tape 14.

Whereas in the foregoing preferred embodiment the construction entails a capstan of a type for drivably moving the edge of a roll of tape, it is to be understood that the term capstan construction of a type for edge driving as used herein and as appearing in the claims shall be deemed to include other annular rotating bodies of a type, for example, such as idler rolls and tape roll followers or other arcuate tape guides such as employed, for example, in the spooling of tape or otherwise.

What is claimed is:

1. A method of constructing a capstan of a type for edgedriving supply and take-up rolls of tape to transfer a length of tape from the former to the latter, said method comprising the steps of forming an annular homogeneous body of material to include a cylindrical periphery having an axial extent substantially coextensive with the width of the tape to be transferred, applying to said body periphery a relatively thin homogeneous layer of resilient material, the width of said layer being greater than the axial extent of said periphery, said layer being dimensioned and disposed to provide end edges of said layer slightly overhanging the ends of said body, disposing a bounding surface of a side wall member against each of the end edges of said layer and compressing said end edges in a direction axially of the body to bulge said layer along the end margins thereof, and thereafter attaching said members to said body to preserve said bulging margins around said capstan.

2. A method of constructing a capstan of a type for edge-driving supply and take-up rolls of tape to transfer a length of tape from the former to the latter, said method comprising the steps of forming an annular hub of rigid matreial to include a cylindrical periphery having an axial extent substantially coextensive with the width of the tape to be transfered, molding to said hub periphery a relatively thin layer of resilient material, the width of said layer being greater than the axial extent of said hub periphery, grinding the end edges of said layer to the plane of the ends of said hub, disposing a bounding surface of a side wall member against each of the end edges of said layer and compressing said end edges in a direction axially of the hub to bulge said layer along the end margins thereof, and thereafter coupling said members to said hub to retain said bulging margins around said capstan.

References Cited UNITED STATES PATENTS 1,837,223 12/1931 Kohlmeier 226- X 1,992,989 3/1935 Burns 226-190 X 3,334,402 8/1967 Cuva 29159 THOMAS H. EAGER, Primary Examiner.

U.S.Cl.X.R. 

